In recent times, conservation of energy has become a paramount concern due to a reduced availability and consequently a high cost of fuel. Conservation measures are particularly needed in the trucking industry.
Modern long-haul trucks are almost universally a tractor and semi-trailer type. In order to obtain as large a volume of load space as possible under regulations limiting a truck's length and width, their design has evolved into a generally rectangular configuration having a large flat-faced frontal area. The front of the tractor cab comprises only a portion of the frontal area, with the remaining frontal area made up of the front surface of the trailer exposed outwardly of the tractor cab. Most tractor-trailer trucks have a large separation between the tractor cab and the front of the trailer which is necessary to allow for movement of the trailer behind the cab during a turn. The large frontal area of the truck and the void space between the tractor and the trailer cause a large wind drag on the truck at highway speeds due to the poor airflow characteristics around the truck's shape. This requires more power to drive the truck and results in substantially increased fuel usage.
Many modifications and accessories have been developed to improve the streamline of the air flow around a combined tractor-trailer truck. Roof-mounted fairings have become popular which generally consist of a curvilinear deflector mounted to the roof of a tractor cab to direct airflow upwardly and over the roof of the trailer rather than allowing air to flow against the exposed upper portion of the forward face of the trailer causing substantial drag.
Additional designs have provided side skirts which are extended between the side of the tractor cab and the side of the trailer to provide a smooth transition surface therebetween. The side skirts streamline airflow past the void space between the tractor and trailer by eliminating turbulence which increases drag on the truck.
Specifically, this invention relates to flexible side panels which extend between a tractor and the trailer which it pulls, to provide improved aerodynamic airflow characteristics.
Exemplarly of prior designs which comprise a roof-mounted fairing and side skirts attached between a tractor and a trailer, is the air flow device disclosed in English Pat. No. 1,532,283, issued to Vauxhall Motors Limited. Side curtains or skirts described therein comprise rectangular sheets of flexible material which are wound around spring-biased rollers mounted to the cab. The material extends rearwardly from the roller for attachment to the side of the trailer to provide a smooth transition surface. The excess material wound on the roller provides let-out and take-up of side curtain material necessary during a turning maneuver of the tractor-trailer truck.
U.S. Pat. No. 4,142,755 of Keedy shows deflector shields extending between the top and sides of a tractor and a trailer to similarly provide a continuous side surface. The deflectors are made of a rigid material and are mounted to a rearward portion of the tractor cab by a hinge for articulating movement. The hinge is spring-biased to maintain sliding contact of the rearward ends of the deflectors with the outer surface of the trailer.
A French patent of Levassor shows a flexible canopy which is attached to the rearward profile of a tow vehicle and which extends rearwardly to conform to the profile of a trailer. The canopy forms a continuous interposing surface. The canopy is held in sliding contact with the trailer surface by springs coupled between the canopy and the periphery of the trailer.
U.S. Pat. No. 4,036,519 of Survais et al describes a shaped inflatable bag positioned between a tractor and a trailer which forms a contoured surface therebetween to improve aerodynamic characteristics. Similarly, the patent of Jenkins, U.S. Pat. No. 4,311,334 and of Cook et al, U.S. Pat. No. 3,834,752 disclose a deflector made of fabric-like material extended between the side surfaces of a tractor and a trailer. The fabric is formed into a bellows-like configuration to provide extensibility which is necessary when the truck makes a turn.
Each of the above cited devices, though providing improvements in the art, have failed to adequately provide an aerodynamic side panel structure which, when combined with a roof-mounted deflector, presents a durable and easy to use apparatus for accomplishing airflow improvement around a tractor-trailer truck. Most approaches disclosed in the prior art comprise fabric materials which are easily damaged in use, have little rigidity to resist deflection, and are difficult to handle for installation. It is often necessary to attach the fabric material to both the tractor cab and the trailer periphery to mount the deflector. This may require that the deflector be made in a custom configuration to fit the application. Other devices have compensated by using very rigid side panels which are difficult to maintain in position and awkward to handle. Some designs require cumbersome tensioning means to maintain the skirt or deflector in position. Many designs have complicated folded patterns or constructions.